Question

what is the role of the calcium oxide (quicklime) in the protein test?

Answer 1

Calcium oxide reacts with protein to break it down into ammonia. The ammonia changes the acidity of the sample, causing a pH change. If protein is present in a food, the litmus paper will change color from red to blue. Also, smell the test tube: If protein is present, you should be able to detect the odor of ammonia. Both of these indicate a positive test for protein. If protein is not present in the test sample (or is in insufficient concentration to produce adequate ammonia during testing), the litmus paper will not turn blue, resulting in a negative test for protein.